Python subprocess get output line by line how to#
empty () def consume ( command ): ''' Example of how to consume standard output and standard error of a subprocess asynchronously without risk on deadlocking. put ( line ) def eof ( self ): '''Check whether there is no more content to expect.''' return not self. _queue = queue def run ( self ): '''The body of the tread: read lines and put them on the queue.''' for line in iter ( self. ''' def _init_ ( self, fd, queue ): assert isinstance ( queue, Queue. Pushes read lines on a queue to be consumed in another thread. Thread ): ''' Helper class to implement asynchronous reading of a file in a separate thread. Import sys import subprocess import random import time import threading import Queue class AsynchronousFileReader ( threading. The standard output and error pipes asynchronously and put each lineĬan then monitor the subprocess by watching the lines as they come in The AsynchronousFileReader class is for the threads that will read In advance from which pipe each line will come. The consume() function, invokes the same script in "child mode"Īs subprocess and monitors its output line by line, without knowing The parent process (script called without arguments), implemented in.Touch of delay simulate a longer running process. Produce() function that just renders some lines randomly on For the child process: when called with 'produce' argument, it runs the.Such a way that is used both for the parent as the child process. The code below shows an example implementation. Separate threads, so one pipe can't block another.
One solution (with limited code and noĭependencies outside the standard library) is to read the pipes in On the web you can find many solutions, with varying degrees of complexity,Ībstraction and dependencies. Line, for example because you want to monitor a longer running process? Which returns the complete standard output and standard error contentįine, but what if you want to read standard output and error line by That's why theĭocumentation recommends the communicate() method,
Python subprocess get output line by line full#
Risk on deadlocks if you are not careful with the order things are done.įor example, you want to read from the subprocess standard output pipe,īut the buffer of the standard error pipe is full and the operating Way (your python process and the child process in this case), is the A tricky issue with having parallel "flows" this To spawn a child/sub process and keep an eye on its standard output Update: I reworked the code below a bit and put it on
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